public void Unregister(EventDelegator delegator)
 {
     delegators.Remove(delegator);
 }
 public void Unregister(EventDelegator delegator)
 {
     delegators.Remove(delegator);
 }
 // Observable Interface
 public void Register(EventDelegator delegator)
 {
     delegators.Add(delegator);
 }
 // Observable Interface
 public void Register(EventDelegator delegator)
 {
     delegators.Add(delegator);
 }